This is an integrated research program in medical oncology focused on oncogenes, viral oncogenesis, growth factors, and their role in human neoplasia. The investigations are of a basic nature, emphasizing human tissues, viruses, and proteins, and the methodologies employed rely heavily on molecular and cell biology and protein analysis and purification. The specific projects are: 1. Comparative Biology of HTLV-I and HTLV-II. 2. Introduction of Macromolecules into Mammalian Cells. 3. Mechanism of Adenovirus Transformation. 4. Viral Trans-acting Transcriptional Regulation. 5. Regulation of Expression of Human Erythroid-potentiating Activity and GM-colony-stimulating Factor. 6. Role of the abl Oncogene in Human Chronic Myelogenous Leukemia. 7. Studies on the Putative Transforming Proteins of the Human T-cell Leukemia Viruses, HTLV-I and HTLV-II. 8. p53: Role in Normal and Malignant Growth and Differentiation. 9. Regulators of Human Macrophage Proliferation and Function: Molecular and Biologic Studies. Each project in this program contributes toward the aim of understanding the biologic basis of neoplasia for the purpose of furthering the general goal of improved prevention and treatment of human cancer.